[PATCH v13 02/11] KVM: VMX: Introduce CET VMCS fields and flags

Yang Weijiang
2020-07-01T08:06:28Z

CET(Control-flow Enforcement Technology) is a CPU feature used to prevent
Return/Jump-Oriented Programming(ROP/JOP) attacks. It provides the following
sub-features to defend against ROP/JOP style control-flow subversion attacks:

Shadow Stack (SHSTK):
A second stack for program which is used exclusively for control transfer
operations.

Indirect Branch Tracking (IBT):
Code branching protection to defend against jump/call oriented programming.

Several new CET MSRs are defined in kernel to support CET:
MSR_IA32_{U,S}_CET: Controls the CET settings for user mode and kernel mode
respectively.

MSR_IA32_PL{0,1,2,3}_SSP: Stores shadow stack pointers for CPL-0,1,2,3
protection respectively.

MSR_IA32_INT_SSP_TAB: Stores base address of shadow stack pointer table.

Two XSAVES state bits are introduced for CET:
IA32_XSS:[bit 11]: Control saving/restoring user mode CET states
IA32_XSS:[bit 12]: Control saving/restoring kernel mode CET states.

Six VMCS fields are introduced for CET:
{HOST,GUEST}_S_CET: Stores CET settings for kernel mode.
{HOST,GUEST}_SSP: Stores shadow stack pointer of current task/thread.
{HOST,GUEST}_INTR_SSP_TABLE: Stores base address of shadow stack pointer
table.

If VM_EXIT_LOAD_HOST_CET_STATE = 1, the host CET states are restored from below
VMCS fields at VM-Exit:
HOST_S_CET
HOST_SSP
HOST_INTR_SSP_TABLE

If VM_ENTRY_LOAD_GUEST_CET_STATE = 1, the guest CET states are loaded from below
VMCS fields at VM-Entry:
GUEST_S_CET
GUEST_SSP
GUEST_INTR_SSP_TABLE

Co-developed-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/include/asm/vmx.h | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 5e090d1f03f8..f301def9125a 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -94,6 +94,7 @@
#define VM_EXIT_CLEAR_BNDCFGS 0x00800000
#define VM_EXIT_PT_CONCEAL_PIP 0x01000000
#define VM_EXIT_CLEAR_IA32_RTIT_CTL 0x02000000
+#define VM_EXIT_LOAD_CET_STATE 0x10000000

#define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR 0x00036dff

@@ -107,6 +108,7 @@
#define VM_ENTRY_LOAD_BNDCFGS 0x00010000
#define VM_ENTRY_PT_CONCEAL_PIP 0x00020000
#define VM_ENTRY_LOAD_IA32_RTIT_CTL 0x00040000
+#define VM_ENTRY_LOAD_CET_STATE 0x00100000

#define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR 0x000011ff

@@ -328,6 +330,9 @@ enum vmcs_field {
GUEST_PENDING_DBG_EXCEPTIONS = 0x00006822,
GUEST_SYSENTER_ESP = 0x00006824,
GUEST_SYSENTER_EIP = 0x00006826,
+ GUEST_S_CET = 0x00006828,
+ GUEST_SSP = 0x0000682a,
+ GUEST_INTR_SSP_TABLE = 0x0000682c,
HOST_CR0 = 0x00006c00,
HOST_CR3 = 0x00006c02,
HOST_CR4 = 0x00006c04,
@@ -340,6 +345,9 @@ enum vmcs_field {
HOST_IA32_SYSENTER_EIP = 0x00006c12,
HOST_RSP = 0x00006c14,
HOST_RIP = 0x00006c16,
+ HOST_S_CET = 0x00006c18,
+ HOST_SSP = 0x00006c1a,
+ HOST_INTR_SSP_TABLE = 0x00006c1c
};

/*
--
2.17.2